The scandal that toppled the high-profile former leadership contender is the biggest political upheaval in China since the general secretary Zhao Ziyang was ousted following the Tiananmen democracy protests in 1989. It comes months before a once-a-decade leadership transition.

The official party newspaper, People's Daily, urged people to rally around the top leadership, saying Bo had damaged the cause and image of both party and state. But while investigations into the couple are ongoing, news coverage also sought to draw a line under events, with a Global Times article saying the country had "steadily overcome a bump" ahead of the 18th party congress this autumn, which will unveil the new leadership.

The news agency Xinhua has said Bo is under investigation by central party officials for "serious disciplinary violations" – a statement that has often been followed by criminal corruption charges against leaders in the past.

Bo was dismissed as party secretary of the south-western city of Chongqing – where Heywood died last November – several weeks ago, but had held on to his politburo and central committee seats, apparently because leaders had not agreed on how to handle him. Many believe that was related to horse-trading before the autumn power transition as well as Bo's powerful connections as the "princeling" son of a renowned Communist party veteran.

The scandal was set in motion in February when Bo's ally and former police chief Wang Lijun fled to the US embassy in Chengdu, where he is believed to have told diplomats he had angered Bo by confronting him with suspicions over Heywood's death. Wang is now under investigation.

But many believe rivals and opponents were already seeking to damage Bo.

Jean-Pierre Cabestan of Hong Kong University suggested Wang's flight, while deeply embarrassing to Chinese leaders, was merely "the last straw on the camel's back". Analysts say Bo alienated senior party figures by attempting to leverage popular support to win promotion in the leadership transition.

"He created a coalition of everyone wanting to get rid of him because he became a 'troublemaker' and a factor of division," said Cabestan.

He suggested it was also "a clear victory for reformists" at the top of the party who are pressing for change.

"Behind this case is a power struggle," said Zhang Ming, a liberal scholar at Renmin University in Beijing.

"Bo broke the rules and greatly deviated from the [usual] track … This shows that the struggle has intensified."

Wu Qiang, a political scientist at Tsinghua University, said Bo's populism had been a threat: "This is a cleaning-up among princelings," he added.

Xinhua has said Bo's 51-year-old wife, Gu Kailai, and a worker from the couple's home are "highly suspected" of killing Heywood. It added that Gu and the couple's son Bo Guagua had been on good terms with the 41-year-old British businessman but that there had been a conflict over economic interests.

Britain had already asked China to reinvestigate the death last November, following suggestions of suspicious circumstances. Family members in China and the UK have dismissed the idea of foul play and said he died of a heart attack.

Heywood's widow was at their home in a blossom-lined, upmarket housing compound in the northern suburbs of Beijing on Tuesday, but did not answer the door. Her late husband's silver Jaguar, bearing a Union Jack sticker, was parked in the driveway.

"No one is home," said a man in plain clothes who said he was head of security for the compound.

Britain and the US were briefed on the announcements shortly before they were made public.

William Hague has welcomed the reinvestigation, telling reporters: "It's a death that needs to be investigated, on its own terms and on its own merits, without political considerations."

Like many developments in the case, Tuesday night's bombshell announcements were presaged by a bout of speculation about such moves on the country's microblogs.

Despite censorship, many used the services to praise and attack Bo on Wednesday.

"Such a good official. He did so many good things for people … How much do the bad guys hate him!" wrote one internet user.

"He wanted to restore the cultural revolution. He even criticised and fought against his own father [during the cultural revolution]. Where is his goodness? I don't get it!" argued another.

A third noted simply: "What happened in Chongqing told us that no matter what is right or wrong, it is important to stand on the winning side."